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Abstract:

A cooling device which is provided with an evaporator with a built-in
wick, a condenser, and a loop type heat pipe which connects the
evaporator and condenser in a loop and is provided with a liquid pipe and
vapor pipe, wherein the evaporator is divided into a liquid-pipe-side
case and a vapor-pipe-side case and wherein a plurality of discharge
ports of working fluids and a wick in which the working fluid from the
discharge ports is completely permeated are arranged between the two
cases. The wick is provided with projecting parts which have recessed
parts corresponding to the discharge ports, while the outer
circumferential surfaces of the projecting parts are provided with
grooves. The working fluid which permeates the wick is changed to a vapor
inside the vapor-pipe-side case, collects in the evaporation chamber, and
is discharged to the liquid pipe, and thus, dry out of the wick is
prevented.

Claims:

1. A cooling device which cools a heat generating member by a loop type
heat pipe, said loop type heat pipe provided with: an evaporator with a
built-in porous member, a condenser, and a liquid pipe and vapor pipe
which connect the evaporator and the condenser in a loop shape, the
cooling device characterized in that said evaporator is provided with a
first case and a second case, said first case is formed by a material
with a low thermal conductivity and runs a working fluid which is
supplied from said liquid pipe through said porous member to send it to
said second case side, said second case is formed by a material with a
high thermal conductivity and is provided with a heat receiving part
which receives heat from said heat generating member, a heating part
which uses the received heat to vaporize said working fluid which seeps
out from said porous member, and a vapor collecting part which collects
vapor of said working fluid and sends it to said vapor pipe, and said
porous member is provided with relief shapes which increase the
permeation area of said working fluid which is sent from said first case
to said second case.

2. The cooling device according to claim 1, wherein said first case is
provided with a storage part of working fluid which distributes and sends
the working fluid which is supplied from said liquid pipe to a plurality
of discharge ports, and said porous member is provided with a flat plate
part, recessed parts which are provided at said first case side of said
flat plate part and which are recessed corresponding to the positions of
said plurality of discharge ports, and projecting parts which are
provided at said second case side of said flat plate part and which
project out corresponding to said recessed parts.

3. The cooling device according to claim 1, wherein said first case is
provided with a storage part of working fluid which is supplied from said
liquid pipe, and said porous member is provided with a flat plate part, a
plurality of recessed parts which are provided at said first case side of
said flat plate part and which are recessed and projecting parts which
are provided at said second case side of said flat plate part and which
project out corresponding to said recessed parts.

4. The cooling device according to claim 2, wherein, the outer
circumferential surfaces of said projecting parts are formed with
pluralities of grooves which run from said first case side to said second
case side, and the distances between bottom surfaces of said grooves and
inner circumferential surfaces of said recessed parts are uniform.

5. The cooling device according to claim 4, wherein said second case is
provided inside it with partition walls which hold said projecting parts,
and end faces of said projecting parts face parts which collect vapor of
said working fluid and send it out to said vapor pipe.

6. The cooling device according to claim 5, wherein inside dimensions of
holding parts of said projecting parts formed by said partition walls are
formed equal to or slightly smaller than outside dimensions of said
projecting parts, and said projecting parts are held in said holding
parts in a compressed state.

7. The cooling device according to claim. 6, wherein said recessed parts
are formed in frusto-conical shapes, and thicknesses of said projecting
parts with said recessed parts are uniform.

8. The cooling device according to claim 6, wherein said recessed parts
are formed in conical shapes, and thicknesses of said projecting parts
with said recessed parts are uniform.

9. The cooling device according to claim 1, wherein said liquid pipe is
connected to said first case at a plurality of locations.

10. The cooling device according to claim 9, wherein said liquid pipe is
branched into two and connected to facing portions of said first case.

11. The cooling device according to claim 10, wherein the parts of said
liquid pipe which are connected to said first case are formed into
further branched pipes.

12. The cooling device according to claim 1, wherein said first case is
provided with a storage part of working fluid which distributes and sends
the working fluid which is supplied from said first case to a plurality
of discharge ports, said porous member is provided with a flat plate
part, projecting parts which are provided at said first case side of said
flat plate part and which project out to be able to fit into said
plurality of discharge ports, and recessed parts which are provided at
said second case side of said flat plate part and which are recessed
corresponding to said projecting parts, and said heating part of said
second case is comprised of columnar parts which are provided sticking
out at the bottom plate of said second case and which fit inside said
recessed parts.

13. The cooling device according to claim 1, wherein said first case is
provided with a storage part of working fluid which is supplied from said
liquid pipe, said porous member is provided with a flat plate part, a
plurality of projecting parts which are provided at said first case side
of said flat plate part and which project out, and recessed parts which
are provided at said second case side of said flat plate part and which
are recessed corresponding to said projecting parts, and said heating
part of said second case is comprised of columnar parts which are
provided sticking out at the bottom plate of said second case and which
fit inside said recessed parts.

14. The cooling device according to claim 12, wherein the inner
circumferential surfaces of said recessed parts are formed with
pluralities of grooves which run from said first case side to said second
case side, and the distances between bottom surfaces of said grooves and
outer circumferential surfaces of said projecting parts are uniform.

15. The cooling device according to claim 14, wherein said recessed parts
are columnar shaped, and said columnar parts which are inserted into said
recessed parts are columns.

16. The cooling device according to claim 2, wherein said storage part of
working fluid is provided inside it with a separator which divides said
storage part into a first storage part and a second storage part and
which is parallel to said flat plate part, and said liquid pipe side of
said first storage part and second storage part is provided with a
connecting part which connects said first storage part and second storage
part.

17. The cooling device according to claim 12, wherein said storage part
of working fluid is provided inside it with a separator which divides
said storage part into a first storage part and a second storage part and
which is parallel to said flat plate part, and said separator is provided
with a through hole which communicates with said porous member which
sticks out into said storage part, said liquid pipe side of said first
storage part and second storage part is provided with a connecting part
which connects said first storage part and second storage part.

18. The cooling device according to claim 2, wherein inside a storage
part of said working fluid, separators which divide said storage part
into a first storage part and a second storage part are provided, said
separators are attached at open ends of said recessed parts at the sides
further from the connecting part of said liquid pipe to said storage part
while being slanted to said connecting part side, and when said
evaporator is arranged standing up vertically with said connecting part
at its upper side, said connecting part side of said separator becomes
said first storage part.

19. The cooling device according to claim 12, wherein, inside a storage
part of said working fluid, separators which divide said storage part
into a first storage part and a second storage part are provided, said
separators are attached at end parts of said porous member at the sides
further from the connecting part of said liquid pipe to said storage part
while being slanted to said connecting part side, when said evaporator is
arranged standing up vertically with said connecting part at its upper
side, said connecting part side of said separator becomes said first
storage part.

20. The cooling device according to claim 1, wherein said first case is
provided with a storage part of the working fluid which is supplied from
said liquid pipe, said porous member is provided with a flat surface at
said first case side and is provided with a plurality of recessed parts
and projecting parts at said second case side, said recessed parts are
parallel groove shapes, said recessed parts provided at said vapor pipe
sides with a connecting space which connects all of the recessed parts
and connects to said vapor pipe, inside a storage part of said working
fluid, a separator which divides said storage part into a first storage
part and a second storage part and which is parallel to said flat surface
is provided, and a connecting part which connects said first storage part
and second storage part is provided at said liquid pipe side of said
first storage part and second storage part.

[0002] The present application relates to a cooling device using a loop
type heat pipe which cools a heat generating member.

BACKGROUND

[0003] As a cooling device which cools an electronic device or other heat
generating member, a heat pipe which circulates a working fluid which is
sealed inside it through a loop shaped pipe and utilizes a phase change
of the working fluid to transport heat is known. In general, a heat pipe
is a cooling device using two-layer flow of a gas and liquid which
circulates a liquid phase cooling solution by using a liquid transport
pump and which makes the cooling solution boil by a cooling device or
heat receiver and uses the latent heat of evaporation to realize a high
cooling performance. A cooling device which uses a liquid transport pump
is suitable when the distance between the heat receiving part and the
heat dissipating part is long and the heat transport distance is large or
when the heat receiving part is made thinner and the flow path is made
narrow like with a microchannel or otherwise when the pressure loss of
the circulating route is large.

[0004] On the other hand, a cooling device using a loop type heat pipe is
known which does not use a liquid transport pump, but uses the capillary
force of a porous member (wick) provided at an evaporator to circulate a
working fluid. A loop type heat pine uses the capillary force of a porous
member in an evaporator to circulate a working fluid, so motive power for
a heat transport pump etc. is not required and the vapor pressure inside
the evaporator can be used to transport heat to a condenser at a distant
location. Such a loop type heat pipe is, for example, disclosed in
Japanese Laid-Open Patent Publication No. 2009-115396A and Japanese
Laid-Open Patent Publication No. 2007-247931A.

[0005] The loop type heat pipe which is disclosed in Japanese Laid-Open
Patent Publication No. 2009-115396A is characterized by an evaporator
structure which has a plurality of wicks inserted in the horizontal
direction and which is thinner and can be increased in evaporation area
(surface area of wicks) compared with the case of a single wick. Further,
the loop type heat pipe which is disclosed in Japanese Laid-Open Patent
Publication No. 2007-247931A is characterized by a structure which has a
wick superposed on a heating surface and which is enlarged in evaporation
area and improved in performance by provision of relief shapes facing the
heating surface and wick.

[0006] However, in the loop type heat pipe which is disclosed in Japanese
Laid-Open Patent Publication No. 2009-115396A, the evaporator is made
thinner, so it is difficult to make the liquid phase working fluid
uniformly permeate the wide area porous member and evaporate, part of the
porous member dries out resulting in circulation of the working fluid
becoming unstable, and the performance fails. Further, in the loop type
heat pipe which is disclosed in Japanese Laid-Open Patent Publication No.
2007-247931A, realizing greater thinness is easy, but when the heat
generating member increases in the amount of heat generated and the
amount of evaporation increases, it becomes harder to supply liquid to
the tip of the wick, dry out occurs, the evaporation area is reduced, and
the cooling performance remarkably falls.

SUMMARY

[0007] In one aspect, the present application has as its object the
provision of a cooling device using a loop type heat pipe which has a
flat plate type evaporator wherein the evaporator can be made thinner
without accompanying dry out of the porous member (wick) or drop in the
cooling performance.

[0008] In another aspect, the present application has as its object the
provision of a cooling device using a loop type heat pipe which has a
flat plate type evaporator wherein the evaporator can function both when
the cooling device is laid on its side horizontally or is arranged
standing up vertically.

[0009] According to one embodiment, there is provided a cooling device
which cools a heat generating member by a loop type heat pipe which is
provided with an evaporator with a built-in porous member, a condenser,
and a liquid pipe and vapor pipe which connect the evaporator and the
condenser in a loop shape, the cooling device characterized in that the
evaporator is provided with a first case and a second case, the first
case is formed by a material with a low thermal conductivity and runs a
working fluid which is supplied from the liquid pine through a porous
member to send it to the second case side, the second case is formed by a
material with a high thermal conductivity and is provided with heat
receiving part which receives heat from the heat generating member, a
heating part which uses the received heat to vaporize the working fluid
which seeps out from the porous member, and a vapor collecting part which
collects vapor of the working fluid and sends it to the vapor pipe, and
the porous member is provided with relief shapes which increase the
permeation area of the working fluid. which is sent from the first case
to the second case.

BRIEF DESCRIPTION OF DRAWINGS

[0010]FIG. 1 is a perspective view in the case where a computer in which
a cooling device using a loop type heat pipe of one embodiment of the
present application is assembled is laid on its side horizontally.

[0011]FIG. 2 is a perspective view which illustrates a first embodiment
of an evaporator which is illustrated in FIG. 1.

[0012]FIG. 3 is a disassembled perspective view which disassembles the
evaporator which is illustrated in FIG. 2 into an upper case and lower
case.

[0013]FIG. 4 is a disassembled perspective view which further
disassembles the upper case and lower case of the evaporator which is
illustrated in FIG. 3.

[0014]FIG. 5A is a plan view of a wick which is illustrated in FIG. 2.

[0015]FIG. 5B is a bottom view of a wick which is illustrated in FIG. 5A.

[0016]FIG. 6A is a cross-sectional view which illustrate the state where
the evaporator which is illustrated in FIG. 4 is placed on a heat
generating member.

[0017]FIG. 6B is an explanatory view which explains movement of the
working fluid in FIG. 6A.

[0018]FIG. 7A is a cross-sectional view which illustrates the same
portion as FIG. 6A which illustrates the structure of a modification of
the first embodiment of an evaporator of sloop type heat pipe of the
present application.

[0019]FIG. 7B is a cross-sectional view which illustrates the same
portion as FIG. 6A which illustrates the structure of another
modification of the first embodiment of an evaporator of a loop type heat
pipe of the present application.

[0020]FIG. 7C is a partially enlarged cross-sectional view which explains
the state of permeation of a working fluid in a wick in another
embodiment which is illustrated in FIG. 7B.

[0021] FIG. 8 is a plan view which illustrates a modification of a liquid
pipe which is connected to an upper case in the first embodiment of an
evaporator of a loop type heat pipe of the present application.

[0022]FIG. 9 is a perspective view which illustrates a second embodiment
of an evaporator of a loop type heat pipe of the present application.

[0023]FIG. 10 is a disassembled perspective view which illustrates the
state of disassembly of the evaporator which is illustrated in FIG. 9
into the upper case and lower case.

[0024] FIG. 11 is a disassembled perspective view which illustrates the
state of further disassembly of the upper case and lower case of the
evaporator which is illustrated in FIG. 10.

[0025]FIG. 12A is a cross-sectional view which illustrates a state where
the evaporator which is illustrated in FIG. 11 is placed on a heat
generating member.

[0027]FIG. 12c is an explanatory view which explains movement of a
working fluid in FIG. 12A.

[0028]FIG. 13 is a disassembled perspective view which illustrates a
third embodiment of an evaporator of a loop type heat pipe of the present
application.

[0029]FIG. 14A is a cross-sectional view which illustrates a state where
the evaporator which is illustrated in FIG. 13 is placed on a heat
generating member.

[0030]FIG. 14B is an explanatory view which explains movement of a
working fluid in FIG. 14A.

[0031]FIG. 14C is a cross-sectional view which illustrates an evaporator
of a cooling device which uses a loop type heat pipe of a modified
embodiment of the third embodiment.

[0032]FIG. 15 is a disassembled perspective view which. illustrates a
fourth embodiment of an evaporator of a loop type heat pipe of the
present application.

[0033]FIG. 16A is a cross-sectional view which illustrates a state where
the evaporator which is illustrated in FIG. 15 is placed on a heat
generating member.

[0034]FIG. 16B is an explanatory view which explains movement of a
working fluid in FIG. 16A.

[0035] FIG. 17 is a perspective view in the case where a computer in which
a cooling device using a loop type heat pipe of one embodiment of the
present application is assembled is arrant standing up vertically.

[0036]FIG. 18A is a cross-sectional view which illustrates a state of use
of the evaporator of the third embodiment which is illustrated in FIG.
14A in the state of use which is illustrated in FIG. 17.

[0037] FIG. 18B is a cross-sectional view which illustrates a state of use
of the evaporator of the fourth embodiment which is illustrated in FIG.
16A in the state of use which is illustrated in FIG. 17.

[0038]FIG. 19A is a cross-sectional view which illustrates a fifth
embodiment of an evaporator of a cooling device which uses a loop type
heat pipe of the present application.

[0039] FIG. 19B is a cross-sectional view which illustrates a sixth
embodiment of an evaporator of a cooling device which use a loop type
heat pipe of the present application.

[0040] FIG. 19C is a front view of a separator which is illustrated in
FIG. 19B.

[0041]FIG. 20A is a cross-sectional view which illustrates a seventh
embodiment of an evaporator of a cooling device which uses a loop type
heat pipe of the present application.

[0042]FIG. 20B is a cross-sectional view which illustrates an eighth
embodiment of an evaporator of a cooling device which uses a loop type
heat pipe of the present application.

[0043]FIG. 20c is a front. view of a separator which is illustrated in
FIG. 20B.

[0044]FIG. 21A is a cross-sectional view which illustrates a ninth
embodiment of an evaporator of a cooling device which uses a loop type
heat pipe of the present application.

[0045] FIG. 21B is a perspective view of a wick which is used in FIG. 21A.

DESCRIPTION OF EMBODIMENTS

[0046] Below, the attached drawings will be used to explain embodiments of
the present application based on specific examples.

[0047]FIG. 1 is a perspective view of electronic equipment, specifically
a computer 50, in which a cooling device 7 using a loop type heat pipe of
one embodiment of the present application is assembled. Note that after
this, the cooling device 7 will also he referred to as the synonymous
"loop type heat pipe 7". The computer 50 includes a circuit board 53
which mounts a plurality of circuit components 52 which include a CPU
(central processing unit) 51, a blowing fan 54 which air cools components
on the circuit hoard 53, power supply 55, and auxiliary storage device
constituted by an HDD (hard disk drive) 56. The components on the circuit
board 53 is cooled by the blowing fan 54, but the high temperature CPU 51
is difficult to be sufficiently cooled by lust the cooling air W, so is
cooled by the loop type heat pipe 7.

[0048] The loop type heat pipe 7 is provided with an evaporator 1 and a
condenser 3. The condenser 3 includes a plurality of heat radiating fins
6. In the present application, the evaporator 1 has a flat plate shape
and is provided with an upper case 1U and a lower case 1L. The upper case
1U and the condenser 3 are connected by a liquid pipe 4 through which a
liquid flows. The lower case 1L and the condenser 3 are connected by a
vapor pipe 5 through which a vapor flows. Further, at the boundary part
of the upper case 1U and the lower case 1L, a wick is provided with
circulates the working fluid of the loop type heat pipe 7 (hereinafter
referred to as the "working fluid"). The evaporator 1 is brought into
close contact with the heat generating component (CPU) 51 on the circuit
board 53 through thermal grease and robs heat from the heat generating
component 51 to cool it.

[0049] The wick is a porous member which is made of a ceramic, metal,
plastic, or other material. The inside of the loop type heat pipe 7 is
completely evacuated, then a water-based, alcohol-based, fluorinated
hydrocarbon compound-based, or other liquid is sealed in it as a working
fluid. In the present application, acetone is used as the working fluid
of the loop type heat pipe 7, the inside of the loop type heat pipe 7 is
evacuated, then a suitable amount of acetone in the saturated state is
sealed inside. The working fluid is heated at the wick of the evaporator
1 to change from a liquid phase working fluid to a vapor which flows
through the vapor pipe 5. It is cooled by the heat radiating fins 6 of
the condenser 3 whereby the vapor becomes a liquid phase working fluid
which is refluxed from the liquid pipe 4 to the evaporator 1. The working
fluid circulates through the inside of the loop type heat pipe 7 due to
the capillary force (capillary tube force) of the wick.

[0050] At the time of operation of the computer 50, an amount of heat of
150 W is generated from the heat generating component 51. This amount of
heat is absorbed by the flat plate type evaporator 1 of the loop type
heat pipe 7. The liquid phase acetone which seeps out from the wick
inside of the evaporator 1 evaporates and vaporizes. The vaporized
acetone vapor moves through the condenser 3 whereby the heat which was
absorbed at the evaporator 1 is transported to the condenser 3. The
acetone vapor which moves through the condenser 3 is cooled and condensed
at the condenser 3 to be liquefied. The amount of heat which is
discharged by the condenser 3 is dissipated from the heat radiating fins
6 and is discharged to the outside of the housing of the computer 50 by
the air which is blown from the fan 54.

[0051]FIG. 2 is a perspective view which illustrates an evaporator 10 of
a first embodiment of the evaporator 1 which is illustrated in FIG. 1.
The outer size of the evaporator 10 of the first embodiment includes, for
example, vertical and horizontal dimensions of 50 mm×50 mm and a
height of 30 mm. The evaporator 10 of the first embodiment is provided
with an upper case 10U to which a liquid pipe 4 is connected and a lower
case 10L to which a vapor pipe 5 is connected. The upper case 10U
includes a cover 11 and a frame 12, while the lower case 10L includes a
wick case 15 which has a built-in wick and a bottom plate 16.

[0052]FIG. 3 is a disassembled perspective view which disassembles the
evaporator 10 which is illustrated in FIG. 2 into an upper case 10U and
lower case 10L. As will be understood from this figure, the wick 14 is
provided at the boundary part of the upper case 10U and the lower case
10L. At the surface of the wick 14 at the upper case 10U side, in the
first embodiment, there are nine lattice-shaped recessed parts 14A. The
recessed parts 14A function as evaporation chambers of working fluid. In
the first embodiment, the number of recessed parts 14A is three in the
vertical direction and three in the horizontal direction for a total of
nine, but the number of recessed parts 14A is not particularly limited.

[0053]FIG. 4 is a disassembled perspective view which further
disassembles the upper case 10U and lower case 10L of the evaporator 10
which is illustrated in FIG. 3. Further, FIG. 6A is a cross-sectional
view which illustrates a longitudinal cross-section of the evaporator 10
of the first embodiment which is explained in FIG. 2 and illustrates the
cross-section at the time of assembly of the parts which are illustrated
in FIG. 4. Therefore, here, FIG. 4 explains the structure of the
evaporator 10 of the first embodiment together with FIG. 6A.

[0054] The upper case 10U is provided with a storage case 13 as a chamber
of the working fluid between the cover 11 and the frame 12. Inside the
storage case 13, there is a storage part 13C of the working fluid. The
height at the inside of the storage case 13 is about 10 mm. The storage
case 13 directly contacts the working fluid, so is made of nylon plastic.
Further, the material of the cover 11 and the frame 12 is stainless steel
with a relatively low thermal conductivity. As a result, leakage of heat
to the working fluid from the storage case 13 is blocked. Furthermore, by
making the material of the cover 11 and frame 12 stainless steel, the
heat from the lower case 10L which contacts the heat generating member is
hardly ever transferred to the working fluid.

[0055] At the bottom surface 130 of the storage case 13 at positions
corresponding to the nine recessed parts 14A at the flat part 14D of the
wick 14, discharge ports 13A of the working fluid are provided. In the
state with the upper case 10U superposed over the lower case 10L, as
illustrated in FIG. 6A, the discharge ports 13A of the storage case 13
are superposed over the openings of the recessed parts 14A of the wick
14. Therefore, the working fluid inside of the storage case 13 completely
flows into the recessed parts 14A of the wick 14 and moves to the lower
case 10L through the wick 14. Further, in the state where the storage
case 13 is held between the cover 11 and the frame 12, the inflow port
13B of the working fluid communicates with the inflow port 12A of the
working fluid which is provided at the frame 12 and the working fluid L
from the liquid pipe 4 which is attached to the inflow port 12A flows
into the storage part 13C as illustrated by the solid line.

[0056] On the other hand, the lower case 10L is provided with a wick case
15 which holds a wick 14 and a bottom plate 16. At the surface of the
wick 14 at the wick case 15 side, projecting parts 14B are provided which
correspond to the recessed parts 14A. The outer dimensions of the
projecting parts 14B may be made 14 mm×14 mm or so and the height
15 mm or so. Further, at the side surfaces of the projecting parts 14B,
for example, grooves of a width 1 mm, depth of 0.5 mm to 1 mm, and pitch
of 2 mm, that is, the grooves 14C, are provided uniformly. The distances
of the outer circumferential surfaces of the projecting parts 146 from
the inner circumferential surfaces of the recessed parts 14A are all the
same. The depths of the grooves 140 are the same at all parts. Therefore,
the thicknesses from the bottom surfaces of the grooves 14C to the
recessed parts 14A are uniform.

[0057]FIG. 5A is a plan view of the wick 14, while FIG. 5B is a bottom
view of the wick 14. The grooves 14C at the side surfaces of the
projecting parts 14B of the wick 14 which is illustrated in FIG. 5B are
drawn by dimensions which are different from the above-mentioned
dimensions so as to exaggeratedly illustrate the shape of the wick 14.
The wick 14 is a made of a porous PTFE (polytetrafluoroethylene) resin
sintered body with a porosity of 40% and an average value of pore
diameters of 20 μm.

[0058] At the lower case 10L, the wick case 15 which is provided at the
bottom side of the wick 14 is provided with a number of wick holding
parts 15B corresponding to the number of the projecting parts 14B which
hold the projecting parts 14B of the wick 14. The depths of the wick
holding parts 15B are the same as the heights of the projecting parts 14B
of the wick 14. In the present embodiment, the wick case 15 is made of
copper with a good thermal conductivity.

[0059] The inner dimensions of the wick holding parts 15B are equal to or
slightly smaller than the outer dimensions of the projecting parts 14B of
the wick 14. The projecting parts 14B of the wick 14 are structured to be
fit into the wick holding parts 15B of the wick case 15 in a slightly
compressed state. That is, to obtain sufficient adhesion with the copper
wick case 15, the dimensions of the projecting parts 14B of the wick 14
should be made equal to the dimensions of the wick holding parts 15B or
larger by about 50 to 200 μm. Further, in the first embodiment, to
obtain sufficient adhesion between the projecting parts 14B of the wick
14 and the wick holding parts 15B of the wick case 15, the side surfaces
where the two contact are vertical to the bottom plate 16.

[0060] At the bottom side of the wick case 15, a bottom plate 16 made of
the same copper which has a good thermal conductivity is provided. At the
top surface of the bottom plate 16, a clearance of 3 mm is provided from
the bottom surface of the wick case 15 to provide a recessed part. This
recessed part is divided by partition walls 16A to form nine evaporation
chambers 17. The openings of the evaporation chambers 17 are superposed
with the wick holding parts 15B. Further, the evaporation chambers 17 are
communicated with adjoining evaporation chambers 17 by connecting holes
18. Further, at the wick case 15 at the outside of the evaporation
chamber 17E which is positioned at the end of the evaporator 10, an
outflow port 19 is provided. The vapor pipe 5 is connected to this
outflow port 19. An evaporator 10 which is provided with the above such
structure is attached on the heat generating member 8 with thermal grease
9 interposed between them.

[0061] Here, the operation of the evaporator 10 of the first embodiment
will be explained using FIG. 6B. In the evaporator 10 of the first
embodiment, the working fluid L which flows in from the liquid pipe 4 to
the storage part 13C of the storage case 13 flows along the bottom
surface 13D of the storage case 13 and is distributed to the insides of
the recessed parts 14A of the wick 14. If the heat generating member 8
generates heat, the heat is transferred, as illustrated by the broken
line H, to the wick case 15 whereby the lower case in rises in
temperature. The working fluid L inside of the recessed parts 14A of the
wick 14, as illustrated by the arrows CP at the parts which face the wick
case 15, permeates the wick 14 by the capillary phenomenon and seeps out
to the grooves 14C. The working fluid L which seeps out to the grooves
14C becomes the vapor V due to the heat of the wick mounting columns 25
which rise in temperature and are connected at the evaporation chambers
17. The vapor V of the working fluid which collects at the evaporation
chambers 17 flows through the connecting holes 18, collects at the
evaporation chamber 17E which is positioned at the end of the evaporator
10 which is illustrated in FIG. 4, and passes through the outflow port 19
to be discharged from the vapor pipe 5.

[0062] In the structure of the evaporator 10 of the first embodiment, as
explained above, the distances from the inner circumferential surfaces of
the recessed parts 14A to the outer circumferential surfaces of the
projecting parts 14B are all the same. Similarly, the distances from the
inner circumferential surfaces of the recessed parts 14A to the bottom
surfaces of the grooves 14C are all the same. Therefore, when the working
fluid L permeates through the wick 14 and collects in the evaporation
chambers 17, since the distances of permeation from the inner
circumferential surfaces of the recessed parts 14A of the wick 14 to the
metal surface (wick case 15) are the same, partial drying hardly ever
occurs at the wick 14. Further, even if heat causes bubbles to occur in
the working fluid L inside the recessed parts 14A of the wick 14, the
bubbles pass through the storage part 13C of the storage case 13, so the
bubbles do not collect inside the recessed parts 14A and partial drying
hardly ever occurs at the wick 14.

[0063] Further, in the evaporator 10 of the first embodiment, as
illustrated in FIGS. 6A and 6B, the contact surfaces CS between the
projecting parts 14B of the wick 14 and the wick holding parts 15B of the
wick case 15 are vertical to the bottom plate 16. As in the modified
embodiment which is illustrated in FIG. 7A, the contact surfaces CS may
also be slanted. If, in this way, making the contact surfaces CS slanted
and making the cross-sectional shapes of the projecting parts 14B
frusto-conical, the projecting parts 14B may easily fit into the wick
holding parts 15B and the assembly of the evaporator 10 becomes easy. The
rest of the structure and operation of the evaporator 10A of the
modification of the evaporator 10 of the first embodiment which is
illustrated in FIG. 7A is the same as the evaporator 10 which is
illustrated in FIG. 6A, so the same members are assigned the same
reference notations and their explanations are omitted.

[0064] Further, as illustrated in FIG. 7B, an evaporator 10B of another
modified embodiment further increased in slant is possible. In the
evaporator 10B which is illustrated in FIG. 7B, the recessed parts 14A of
the wick 14 are not frusto-conical in shape but are made conical in shape
with the bottom surfaces of the recessed parts 14A eliminated, so the
entire inner circumferential surfaces of the recessed parts 14A of the
wick 14 face the wick case 15. For this reason, if the heat H which is
transferred from the heating surface of the bottom plate 16 is
transferred to the wick case 15 and the contact surfaces CS are heated,
permeation from the entire inner circumferential surfaces of the recessed
parts 14A occurs due to the capillary phenomenon as illustrated by the
arrows CP. At this time, the depths of the grooves 14C are uniform, so
the distances of permeation of the working fluid L also become uniform.
The structure of the other parts of the evaporator 10B is the same as
that of the evaporator 10A which is illustrated in FIG, 7A, so the same
members are assigned the same reference notations and their explanations
are omitted.

[0065] On the other hand, in the evaporators 10, 10A, 10B of the first
embodiment, the case may be considered where the working fluid L which is
supplied from the liquid pipe 4 does not evenly collect inside all of the
recessed parts 14A of the wick 14. In such a case, as illustrated by the
modification which is illustrated in FIG. 8, manifolds M1 and M2 may be
attached to the facing surfaces of the evaporator 10, the manifold M1 may
be connected to the liquid pipe 4, and the manifold M2 may be connected
to the branch pipe 4A which is branched from the liquid pipe 4.

[0066] An experiment was conducted in which a loop type heat pipe which
uses the evaporator 10 of the first embodiment was attached inside the
electronic equipment and the electronic device (CPU) inside the operating
electronic equipment was cooed. As a result, it was learned that even in
the state where the electronic device operates at a maximum speed and the
amount of heat generated is about a maximum 150 W, the junction
temperature is held at 60° C. or less and good cooling is
possible. Further, it was learned that under all conditions, including
the state where the electronic equipment is operating at full capacity,
the wick 14 in the evaporator 10 wilt not dry out, the electronic device
will not become an abnormally high temperature, and stable cooling
performance is obtained. In this way, if using the thin, type,
plate-shaped evaporator 10 of the first embodiment for the loop type heat
pipe, a high heat generating member will be efficiently cooled and the
electronic equipment or computer becomes higher in performance.

[0067]FIG. 9 is a perspective view which illustrates an evaporator 20 of
a second embodiment of the evaporator 1 which is illustrated in FIG. 1.
The outer size of the evaporator 20 of the second embodiment includes,
for example, vertical and horizontal dimensions of 50 mm×50 mm and
a height of 30 mm. The evaporator 20 of the second embodiment is provided
with an upper case 20U to which a liquid pipe 4 is connected and a lower
case 20L to which a vapor pipe 5 is connected. The upper case 20U
includes a cover 21 and a frame 22, while the lower case 20L includes a
bottom plate 26 which has a built-in wick.

[0068]FIG. 10 is a disassembled perspective view which disassembles the
evaporator 20 which is illustrated in FIG. 9 into an upper case 20U and a
lower case 20L. As will be understood from FIG. 10, the wick 14 is
provided at the boundary part of the upper case 20U and the lower case
20L. At the flat part 24D at the upper case 20U side of the wick 24, in
the second embodiment, there are nine columnar shaped projecting parts
24B. The wick 24 has the function of making the working fluid evaporate
to obtain a vapor. In the second embodiment, the number of the projecting
parts 24B at the wick 24 is three in the vertical direction and three in
the horizontal direction for a total of nine, but the number of the
projecting parts 24B is not particularly limited.

[0069] FIG. 11 is a disassembled perspective view which further
disassembles the upper case 20U and the lower case 20L of the evaporator
20 which is illustrated in FIG. 10. Further, FIG. 12A is a
cross-sectional new which illustrates a longitudinal cross-section of the
evaporator 20 of the second embodiment which is explained in FIG. 9 and
illustrates a cross-section at the time of assembly of the members which
are illustrated in FIG. 11. Therefore, here, FIG. 11, together with FIG.
12A, explains the structure of the evaporator 20 of the second
embodiment.

[0070] The upper case 20U is provided with a storage case 23 as a chamber
of the working fluid between the cover 21 and the frame 22. Inside the
storage case 23, there is a storage part 23C of the working fluid. The
height at the inside of the storage case 23 is about 10 mm. The storage
case 23 directly contacts the working fluid, so is made of nylon plastic.
Further, the material of the cover 21 and the frame 22 is stainless steel
with a relatively low thermal conductivity. As a result, it is hard for
heat to be transferred from the outside through the storage case 23 to
the working fluid at the inside. Furthermore, by making the material of
the cover 21 and frame 22 stainless steel, the heat from the lower case
20L which contacts the heat generating member hardly ever is transferred
to the storage case 23.

[0071] At the bottom surface 23D of the storage case 23 at positions
corresponding to the nine pro coning parts 24B at the wick 24, discharge
ports 23A of the working fluid are provided. In the state with the upper
case 20U superposed over the lower case 20L, as illustrated in FIG. 12A,
the protecting parts 24B of the wick 24 are inserted through the
discharge ports 23A of the storage case 23 and stick out into the storage
part 23C of the storage case 23. There is no clearance between the outer
circumferential surfaces of the projecting parts 24B and the inner
circumferential surfaces of the discharge ports 23A, so the working fluid
inside of the storage case 23 permeates to all of the projecting parts
24B of the wick 24 and passes through the wick 24 to move to the lower
case 20L. Further, in the state where the storage case 23 is held between
the cover 21 and the frame 22, the inflow port 23B of the working fluid
communicates with the inflow port 22A of the working fluid which is
provided at the frame 22 and the working fluid L from the liquid pipe 4
which is attached to the inflow port 22A flows into the storage part 23C
as illustrated by the solid line.

[0072] On the other hand, the lower case 20L is provided with a bottom
plate 26 which is provided with a recessed part 27 forming an evaporation
chamber (hereinafter referred to as the "evaporation chamber 27") and
wick mounting columns 25 which are provided sticking out at the
evaporation chamber 27. There are nine wick mounting columns 25. The
center axes of the wick mounting columns 25 are aligned with the center
axes of the nine column-shaped projecting parts 24B of the wick 24. The
depth of the evaporation chamber 27 may be made about 3 mm, the diameters
of the wick mounting columns 25 may be made φ9 mm, and the heights
may be made 15 mm. Further, at one end of the bottom plate 26, there is
an outflow port 29 which is connected to the evaporation chamber 27. The
vapor pipe 5 is connected to the outflow port 29. In the present
embodiment, the wick mounting columns 25 and the bottom plate 26 are made
of copper with good thermal conductivity. Further, the bottom plate 26 is
attached on the heat generating member 8 with thermal grease 9
interposed.

[0073] The wick 24 may be made a porous PTFE (polytetrafluoroethylene)
resin sintered body with a porosity of 40% and an average value of pore
diameters of 20 μm. Further, at the back surface of the projecting
parts 24B of the wick 24, recessed parts 24A in which the wick mounting
columns 25 which are provided sticking out from the bottom plate 26 are
inserted are provided. The recessed parts 24A, as will be understood from
FIG. 12B which illustrates a cross-section along the line B-B which is
illustrated in FIG. 12A, are shaped provided with grooves 24C at equal
intervals in their inner circumferential surfaces into which the wick
mounting columns 25 are inserted. The inside diameters of the inner
circumferential surfaces of the recessed parts 24A may be made φ9 mm,
the depths 12 mm, and the outside diameters of the projecting parts of
the wick 24 φ13 mm. Therefore, in the state with the wick mounting
columns 25 inserted into the recessed parts 24A of the wick 24, the
surface of the wick 24 at the bottom plate side becomes positioned on the
same plane as the end face 26A of the bottom plate 26.

[0074] The grooves 24C, for example, may be uniformly provided at the
inner circumferential surfaces of the recessed parts 24A with widths of 1
mm, depths of 1 mm, and a pitch of 2 mm in a direction vertical to the
bottom plate 26. With this configuration, the thicknesses from the bottom
surfaces of the grooves 24C to the outer circumferential surfaces of the
projecting parts 24B of the wick 24 are uniform. However, the grooves 24C
at the inner circumferential surfaces of the recessed parts 24A of the
wick 24 which is illustrated in FIG. 12B are drawn by dimensions
different from the above-mentioned dimensions so as to exaggeratedly
illustrate the shapes of the recessed parts 24A of the wick 24. Further,
the inside diameters of the inner circumferential surfaces of the
recessed parts 24A in which the wick mounting columns 25 are inserted may
be fabricated to be equal to the outside diameter dimensions of the wick
mounting columns 25 or 50 to 200 μm or so smaller so as to obtain
sufficient fit with the wick mounting columns 25.

[0075] Here, FIG. 12c will be used to explain the operation of the
evaporator 20 of the second embodiment. In the evaporator 20 of the
second embodiment, the working fluid L which flows from the liquid pipe 4
to the storage part 23C of the storage case 23 collects uniformly around
the projecting parts 24B of the wick 24 whereby in permeates along the
outer circumference surfaces of the projecting parts 24B of the wick 24.
If the heat generating member 8 generates heat, the heat is transferred
to the wick mounting columns 25 as illustrated by the broken line H and
the wick mounting columns 25 rise in temperature. The working fluid L at
the outside of the projecting parts 24B of the wick 24, as illustrated by
the arrows CP, permeate through the wick 24 by the capillary phenomenon
and seep out to the grooves 24C. The working fluid L which seeps out to
the grooves 24C is heated by the heat of the wick mounting columns 25 to
become vapor V which collects at the evaporation chamber 27. As explained
above, the thicknesses from the bottom surfaces of the grooves 24C to the
outer circumferential surfaces of the projecting parts 24B of the wick 24
are uniform, so the distances of permeation of the working fluid L become
uniform. The vapor V of the working fluid which collects at the
evaporation chamber 27 passes through the outflow port 29 and is
discharged from the vapor pipe 5.

[0076] In the structure of the evaporator 20 of the second embodiment,
when the working fluid L permeates through the wick 24, then becomes a
vapor V which collects at the evaporation chamber 27, since the distances
of permeation from the projecting parts 24B of the wick 24 to the metal
surfaces (wick mounting columns 25) are the same, partial drying hardly
ever occurs at the wick 24. Further, the areas around the projecting
parts 24B of the wick 24 form a continuous structure in the same plane,
so the projecting parts 24B are uniformly supplied with working fluid.
That is, the bottommost parts of the wick 24 are closest to the bottom
surface of the evaporator 20 and easily become high in temperature, but
the wick 24 reliably permeates the working fluid L, so it is possible to
completely prevent partial drying or dry out of the wick 24. For this
reasons, it is possible to realize more highly reliable operability.

[0077] In the second embodiment, ethanol was used as the working fluid. An
experiment was conducted which used a loop type heat pipe using an
evaporator 20 of the second embodiment to cool an electronic device (CPU)
in an operating electronic equipment. As a result, it was learned that
even in a state where the electronic device is operating at maximum speed
and the amount of heat generation is about the maximum 150 W, the
junction temperature was held at 55° C. or less and good cooling
was possible. Further, it was learned that under all conditions,
including the state where the electronic equipment is operating at full
capacity, the wick 24 in the evaporator 20 will not dry out, the
electronic device will not become an abnormally high temperature, and
stable cooling performance is obtained. In this way, in a cooling device
using a loop type heat pipe which has a thin type, plate-shaped
evaporator 20 of the second embodiment, a high heat generating member
will be efficiently cooled and the electronic equipment or computer
becomes higher in performance,

[0078]FIG. 13 is a disassembled perspective view which illustrates an
evaporator 10A of a third embodiment of the loop type heat pipe of the
present application. The component members of the evaporator 10A of the
third embodiment are almost the same as the component members of the
evaporator 10 of the first embodiment which was explained from FIG. 2 to
FIG. 6. Accordingly, the same component members are assigned the same
reference notations and their explanations are omitted.

[0079] In the structure of the evaporator 10A of the third embodiment, the
only point of difference from the structure of the evaporator 10 of the
first embodiment is the structure of the storage case 13. The storage
case 13 in the evaporator 10 of the first embodiment is provided with
discharge ports 13A of working fluid at positions corresponding to the
nine recessed parts 14A at the flat part 14D of the wick 14 at the bottom
surface 13D. On the other hand, in the evaporator 10A of the third
embodiment, the storage case 13 has no bottom surface 13D. As illustrated
in FIG. 14A, the surface which faces the wick 14 is completely open.
Therefore, the working fluid which flows into the storage case 13 flows
over the flat part 14D of the wick 14 and flows into the recessed parts
14A.

[0080]FIG. 14B is an explanatory view which explains the movement of the
working fluid in FIG. 14A. In the evaporator 10A of the third embodiment
as well, the working fluid L which flows in from the liquid pipe 4 to the
storage part 13C of the storage case 13 flows over the flat part 14D of
the wick 14 and is distributed to the insides of the recessed parts 14A.
If the heat generating member 8 generates heat, the heat is transferred
to the wick case 15 as illustrated by the broken line and the lower case
10L rises in temperature. Due to the rise in temperature of the lower
case 10L, the working fluid L in the recessed parts 14A of the wick 14
permeates through the wick 15 by the capillary phenomenon as illustrated
by the capillary phenomenon and seeps out to the grooves 14C. The working
fluid L which seeps out to the grooves 14C is heated by the heat of the
wick case 15 to become the vapor V which collects in the evaporation
chambers 17. The vapor V of the working fluid which collects in the
evaporation chambers 17 flows through the connecting holes 18, collects
at the evaporation chamber 17E which is positioned at the end of the
evaporator 10 which is illustrated in FIG. 4, and passes through the
outflow port 19 to be discharged from the vapor pipe 5.

[0081] In the structure of the evaporator 10A of the third embodiment,
before the working fluid L flows into the recessed parts 14A of the wick
14, it passes over the flat part 14D of the wick 14. At this time, the
working fluid L permeates slightly into the flat part 14D of the wick 14,
so in the structure of the evaporator 10A of the third embodiment,
partial drying of the flat part 14D of the wick 14 hardly ever occurs.

[0082] For the structure of the evaporator 10A of the third embodiment,
the structure which is illustrated in FIG. 13C similar to the evaporator
10B of the modified embodiment which is explained in FIG. 7B is possible.
That is, as illustrated in FIG. 14C, an evaporator 10B of a modified
embodiment which further increases the slant of the contact surfaces CS
with the wick case 15 of the wick 14 is possible. The structure of the
evaporator 10B which is illustrated in FIG. 14C differs from the
structure of the evaporator 10A which is illustrated, in FIG. 14A in only
the shape of the wick 14. The explanation of the different parts is the
same as with FIG. 7B, so the same members are assigned the same reference
notations and their explanations are omitted.

[0083]FIG. 15 is a disassembled perspective view which illustrates an
evaporator 20A of a fourth embodiment of a loop type heat pipe of the
present application. The component members of the evaporator 20A of the
fourth embodiment are almost the same as the component members of the
evaporator 20 of the second embodiment which is explained from FIG. 9 to
FIG. 12. Accordingly, the same component members are assigned the same
reference notations and their explanations are omitted.

[0084] In the structure of the evaporator 20A of the fourth embodiment,
the only point of difference from the structure of the evaporator 20 of
the second embodiment is the structure of the storage case 23. The
storage case 23 in the evaporator 20 of the second embodiment is provided
with discharge openings 23A of the working fluid corresponding to the
projecting parts 24B of the wick 24 at its bottom surface 23D. On the
other hand, in the evaporator 20A of the fourth embodiment, the storage
case 23 has no bottom surface 23D. As illustrated in FIG. 16A, the
surface facing the wick 24 is completely open. Therefore, the working
fluid which flows into the storage case 23 contacts the side surfaces of
the projecting parts 24B of the wick 24 and contacts the fiat part 24D
around the projecting parts 24B of the wick 24.

[0085]FIG. 16B is an explanatory view which explains movement of the
working fluid L in FIG. 16A. In the evaporator 20A of the fourth
embodiment as well, the working fluid L which flows in from the liquid
pipe 4 to the storage part 23C of the storage case 23 uniformly collects
around the projecting parts 24B of the wick 24 and permeates to the outer
circumferential surfaces of the projecting parts 24B and flat part 24D of
the wick 24. If the heat generating member 8 generates heat, the heat is
transferred to the wick mounting columns 25 as illustrated by the broken
line. Due to the temperature rise of the wick mounting columns 25, the
working fluid L at the outsides of the projecting parts 24B of the wick
24 permeates through the wick 24 and seeps out to the grooves 24V by the
capillary phenomenon as illustrated by the arrows. The working fluid L
which seeps out to the grooves 24C becomes vapor V by the heat of the
wick mounting columns 25 and collects at the evaporation chamber 27. The
thicknesses from the bottom surfaces of the grooves 24C to the outer
circumferential surfaces of the projecting parts 24B of the wick 24 are
uniform, so the distances of permeation of the working fluid L are equal.
The vapor V of the working fluid which collects at the evaporation
chamber 27 is ejected through the outflow port 29 from the vapor pipe 5.

[0086] In the structure of the evaporator 20A of the fourth embodiment,
the working fluid L permeates to the flat part 24D of the wick 24 as well
and collects at the evaporation chamber 27, so partial drying of the flat
part 24D of the wick 24 hardly ever occurs. Further, the areas around the
projecting parts 24B of the wick 24 form a continuous structure in the
same plane, so the projecting parts 24B are uniformly supplied with
working fluid. That is, the bottom part and flat part 24D of the wick 24
are the closest to the bottom surface of the evaporator 20 and easily
become high in temperature, but the wick 24 is reliably impregnated with
the working fluid L, so partial drying and dry out of the wick 24 is
completely prevented. For this reason, more highly reliable operability
is possible to be realized.

[0087] As explained above, according to the evaporator of a loop type heat
pipe of the present application, the distances of permeation to the metal
surface inside of the recessed parts of the wick or the porous members of
the projecting parts become uniform, so partial drying of the wick hardly
ever occurs and "dry out" where the wick dries out will never occur.
Further, in the temperature distribution of the wick, the parts near the
evaporator bottom surface become high in temperature, so the working
fluid evaporates in a large amount from the tip of the wick close to the
evaporator bottom surface, but according to the evaporator structure of
the present application, the tip of the wick is positioned at the lowest
point ac the liquid chamber side, so the tip of the wick is most easily
supplied with working fluid.

[0088] Furthermore, by using an elastic plastic porous member for the
wick, it is possible obtain a structure in which the side surfaces of the
wick are in close contact with the recessed part of the evaporator bottom
surface or the side surfaces of the projecting parts, so it is possible
to efficiently transfer the heat of the bottom surface of the evaporator
to the wick and possible to realize a high cooling performance. In this
way, in the cooling device using a loop type heat pipe which uses the
evaporator structure of the present application, at the time of high heat
generation of a heat generating component, it is possible to obtain a
stable cooling performance without a drop in the amount of heat
generation of the evaporator.

[0089] In this regard, the computer 50 which is illustrated in FIG. 1 is
generally used in a state laid flat (laid horizontally) but due to the
space restrictions on a desk, the computer 50 is sometimes used in a
state arranged standing up vertically as illustrated in FIG. 17. In such
a case, in the above-mentioned evaporators of the first to fourth
embodiments, at the time of low heat generation where the inside of the
evaporator is not filled with working fluid, a state ends up occurring
where the wick is not sufficiently supplied with working fluid. This
issue will be explained using FIG. 18 using the third and fourth
embodiments as examples.

[0090]FIG. 18A is a cross-sectional view which illustrates the state of
use of the evaporator 10A of the third embodiment which is illustrated in
FIG. 14A in the state of use which is illustrated in FIG. 17. If the
computer 50 is arranged standing up vertically, the evaporator 10A is
also arranged standing up vertically, so at the time of low heat
generation where the inside of the evaporator is not filled with the
working fluid, the working fluid L collects at the bottom part of the
storage part 13C of the evaporator 10A and a part is formed where working
fluid L is not supplied at the top part of the evaporator 10A. For this
reason, it becomes difficult to supply working fluid to the top end part
of the wick 14 and dry out easily occurs at the wick. This issue, as
illustrated in FIG. 18B, is the same even in the case where the
evaporator 20A of the fourth embodiment which is illustrated in FIG. 16A
is arranged standing up vertically.

[0091] To deal with this issue, in the present application, by providing
separators inside of the evaporators of the first to fourth embodiments,
even if the evaporator is arranged standing up, the working fluid which
is filled inside of the evaporator is evenly supplied to the wick inside
of the evaporator. Several embodiments in which separators are provided
inside the evaporators will be explained using FIG. 19 to FIG. 21.

[0092]FIG. 19A illustrates an evaporator 10C of a fifth embodiment of a
loop type heat pipe of the present application. The evaporator 10C of the
fifth embodiment comprises the evaporator 10A of the third embodiment
which is illustrated in FIG. 14A inside of which a separator 61 is
provided. The rest of the configuration other than the separator 61 is
the same as the evaporator 10A of the third embodiment, so the same
members are assigned the same reference notations and their explanations
are omitted. The separator 61 is a flat plate shape, is attached inside
of the storage case 13 in parallel to the cover 11, and divides the
storage part of the working fluid into a first storage part 13C1 and a
second storage part 13C2. The separator 61 is provided inside of the
storage case 13 so that the first storage part 13C1 is positioned
immediately below the inflow port 13B of the working fluid L from the
liquid pipe 4 at the storage case 13 at the time when the evaporator 10C
is arranged standing up vertically. The total length of the separator 61
in the vertical direction is smaller than the inner dimension of the
storage case 13 in the vertical direction, so at the top end of the
separator 61, a connecting space 13C3 is provided which connects the
first storage part 13C1 and the second storage part 13C2. Due to the
connecting space 13C3, the working fluid L moves between the first
storage part 13C1 and the second storage part 13C2. Further, at the
bottom end part of the separator 61, a fine hole 61A is provided which
connects the first storage part 13C1 and the second storage part 13C2.

[0093] If the above configured evaporator 10C is arranged standing up
vertically, the working fluid L which passes through the liquid pipe 4
and flows in from the inflow port 13B to the inside of the storage case
13 collects inside the first storage part 13C1 partitioned by the
separator 61. The volume of the first storage part 13C1 is smaller than
the storage case 13 as a whole, so even at the time of low heat
generation where the inside of the evaporator is not filled with working
fluid, the working fluid L fills the first storage part 13C1. For this
reason, all of the wick 14 is supplied with working fluid L from the
first storage part 13C1 and the wick 14 not longer suffers dry out. Note
that, after the first storage part 13C1 is filled full with the working
fluid L, the working fluid overflows from the first storage part 13C1 and
collects at the second storage part 13C2. The evaporator 10C of the fifth
embodiment is provided with the connecting space 13C3 which connects the
first storage part 13C1 and the second storage part 13C2, so in the state
where the computer is laid fiat horizontally, the evaporator operates in
the same way as the evaporator 10A of the third embodiment.

[0094] FIG. 19B illustrates an evaporator 20C of a sixth embodiment of the
loop type heat pipe of the present application. The evaporator 20C of the
sixth. embodiment provides a separator 62 inside of the evaporator 20A of
the fourth embodiment which is illustrated in FIG. 16A. The rest of the
configuration other than the separator 62 is the same as the evaporator
20A of the fourth embodiment, so the same members are assigned the same
reference notations and their explanations are omitted. The separator 62,
as illustrated in FIG. 19C, is a flat plate shape and is provided with
circular holes 62A and semicircular recessed parts 62B equal to the outer
shapes of the wick 24 at positions corresponding to the wick 24. The
separator 62, in the state where the evaporator 20C is arranged standing
up vertically, is attached inside of the storage case 23 parallel to the
cover 21 in the state with circular holes 62A fit over the bottom sides
of the wick 24 and with the semicircular recessed parts 62B fit over the
bottom sides of the topmost stage of the wick 24.

[0095] The mounting position of the separator 62 is at the side close to
the front ends of the projecting parts 24B of the wick 24. The separator
62 is used to divide the storage part of the working fluid into the first
storage part 23C1 and the second storage part 23C2. Further, the
separator 62 is provided inside of the storage case 23 so that the first
storage part 23C1 is positioned directly under the inflow port 23B of the
working fluid L from the liquid pipe 4 in the storage case 23 when the
evaporator 20C is arranged standing up vertically. The total length of
the separator 62 in the vertical direction is smaller than the inner
dimension of the storage case 23 in the vertical direction. At the top
end. of the separator 62, therefore, a connecting space 23C3 which
connects the first storage part 23C1 and the second storage part 2302 is
provided to enable movement of working fluid L.

[0096] If the thus configured evaporator 20C is arranged standing up
vertically, the working fluid L which passes through the liquid pipe 4
and flows from the inflow port 23B to the inside of the storage case 23
collects inside the first storage part 23C1 which is formed by
partitioning by the separator 62. The volume of the first storage part
23C1 is smaller than the volume of the storage case 23 as a whole, so
even at the time of low heat generation when the inside of the evaporator
is not filled with the working fluid, the working fluid L fills the first
storage part 23C1. For this reason, all of the wick 24 is supplied with
working fluid L from the first storage part 23C1 and the wick 24 no
longer suffers from dry out. Note that, after the first storage part 23C1
is filled full with the working fluid L, the working fluid overflows from
the first storage part 23C1 and collects at the second storage part 23C2.
The evaporator 20C of the sixth embodiment is provided with a connecting
space 23C3 which connects the first storage part 23C1 and the second
storage part 23C2, so in the state where the computer is laid flat
horizontally, the evaporator operates in the same way as the evaporator
20A of the fourth embodiment.

[0097]FIG. 20A illustrates an evaporator 10D of a seventh embodiment of a
loop type heat pipe of the present application. The evaporator 10D of the
seventh embodiment provides separators 71 inside of the evaporator 10A of
the third embodiment which is illustrated in FIG. 14A. The rest of the
configuration other than the separators 71 is the same as the evaporator
10A of the third embodiment, so the same members are assigned the same
reference notations and their explanations are omitted. The separators 71
are flat plate shapes which are arranged inside the storage case 13 at a
slant by being made to tilt upward at a boundary part of the first stage
and second stage and a boundary part of the second stage and third stage
of the recessed parts 14A of the wick arranged in the horizontal
direction. The separators 71 are provided inside of the storage case 13
so that the separators 71 are positioned directly under the inflow port
13B of the working fluid L from the liquid pipe 4 at the storage case
when the evaporator 10D is arranged standing up vertically. The first
storage part 13C1 is a part which is formed by the separator 71 and has
working fluid L collected in it. The remaining space of the storage case
13 is the second storage part 13C2.

[0098] If the thus configured evaporator 10D is arranged standing up
vertically, the working fluid L which flows through the liquid pipe 4
from the inflow port 13B to the inside of the storage case 13 is received
by the separator 71 at the topmost stage and collects inside the first
storage part 13C1. The volume of the first storage part 13C1 is small, so
the inside of the topmost stage first storage part 13C1 immediately
becomes filled with the working fluid L and the overflowing working fluid
L collects at the second first storage part 13C1. The volume of the
second first storage part 13C1 is also small, so the inside of the second
first storage part 13C1 also immediately becomes filled with the working
fluid L and the overflowing working fluid L collects at the bottom part
of the storage case 13. For this reason, all of the stages of the wick 14
are supplied with working fluid L and the wick 14 no longer suffers from
dry out. In the evaporator 10D of the seventh embodiment, the first
storage part 13C1 and the second storage part 13C2 are connected, so in
the state where the computer is laid flat horizontally, the evaporator
operates in the same way as the evaporator 10A of the third embodiment.

[0099]FIG. 20B illustrates an evaporator 20D of an eighth embodiment of a
loop type heat pipe of the present application. The evaporator 20D of the
eighth embodiment is provided with separators 72 inside of the evaporator
20A of the fourth embodiment which is illustrated in FIG. 16A. The rest
of the configuration other than the separators 72 is the same as the
evaporator 20A of the fourth embodiment, so the same members are assigned
the same reference notations and their explanations are omitted. The
separators 72, as illustrated in FIG. 20c, are flat plate shapes, are
bent to the top side at the ends at the wick 24 side, and are provided
with semicircular recessed parts 72A at the bent parts. The separators
72, in the state where the evaporator 20D is arranged sanding up
vertically, are attached at a slant with the flat plate parts tilted
upward with the semicircular recessed parts 72A fit over the bottom sides
of the topmost stage and second stage wicks 24. The separators 72 are
provided inside of the storage case 23 so that they are positioned right
under the inflow port 23B of the working fluid L from the liquid pipe 4
at the storage case when the evaporator 20D is arranged standing up
vertically. The first storage part 23C1 is a part which is formed by a
separator 72 where the working fluid L collects. The remaining space of
the storage case 23 is the second storage part 23C2.

[0100] If the thus configured evaporator 20D is arranged standing up
vertically, the working fluid L which flows through the liquid pipe 4
from the inflow port 23B to the inside of the storage case 23 is received
by the separator 72 at the topmost stage and collects inside the first
storage part 23C1. The volume of the first storage part 23C1 is small, so
the inside of the topmost stage first storage part 23C1 immediately
becomes filled with the working fluid L and the overflowing working fluid
L collects at the second first storage part 23C1. The volume of the
second first storage part 23C1 is also small, so the inside of the second
first storage part 23C1 also immediately becomes filled with the working
fluid L and the overflowing working fluid L collects at the bottom part
of the storage case 23. For this reason, all of the stages of the wick 24
are supplied with working fluid L and the wick 24 no longer suffers from
dry out. In the evaporator 20D of the second embodiment, the first
storage part 23C1 and the second storage part 23C2 are connected, so the
evaporator 20A of the fourth embodiment operates in the same way in the
state where the computer is laid flat horizontally.

[0101]FIG. 21A illustrates an evaporator 10E of a ninth embodiment of a
loop type heat pipe of the present application, while FIG. 21B is a
perspective view of a wick 34 which is used in FIG. 21A. The structure of
the evaporator 10E of the ninth embodiment differs from the structures of
the evaporators of the first to eighth embodiments. The evaporator 10E of
the ninth embodiment is provided with a cover 31, frame 32, and bottom
plate 36. The liquid pipe 4 and the vapor pipe 5 are connected to the
side surface of the frame 32. FIG. 21A illustrates the state where the
evaporator 10E is arranged standing up vertically. In this state, the
wick 33 which is provided with the connecting space 34A and the grooves
34C such as illustrated in FIG. 21B is attached to the frame 32 so that
the connecting space 34A adjoins the outflow port 39. Further, inside of
the frame 32, a separator 61 similar to the seventh embodiment is
provided. The configuration of the separator 61 is similar to that of the
seventh embodiment, so the same reference notations are assigned and
further explanation is omitted. Note that, in the evaporator 10E of the
ninth embodiment, the description of the storage case is omitted, but a
storage case may also he provided inside of the cover 23 in the same way
as the first to the eighth embodiments.

[0102] If the evaporator 10E which was configured in the above way is
arranged standing up vertically, the working fluid L which passes through
the liquid pipe 4 from the inflow port 32A to the inside of the
evaporator 10E collects inside the first storage part 33C1 formed by
partitioning by the separator 61. The volume of the first storage part
33C1 is smaller than the volume of the evaporator 10E as a whole, so even
at the time at low heat generation where the inside of the evaporator 10E
is not filled with working fluid L, the working fluid L fills the first
storage part 33C1. For this reason, working fluid L is supplied to the
majority of the surface of the wick 34 from the first storage part 33C
and dry out no longer occurs at the top part of the wick 34. The working
fluid L which permeates through the wick 34 and seeps out to the insides
of the grooves 34C becomes the vapor V due to the heat from the bottom
plate 36 and flows from the outflow port 39 to the vapor pipe 5. Note
that after the first storage part 33C1 is filled with working fluid L,
the working fluid L overflows from the first storage part 33C1 and
collects in the second storage part 33C2. The evaporator 10E of the ninth
embodiment is provided with a connecting space 33C3 which connects the
first storage part 33C1 and the second storage part 33C2, so operates in
the same way even if the computer is laid flat horizontally.

[0103] Although only some exemplary embodiments of this invention have
been described in detail above, those skilled in the art will readily
appreciate that many modifications are possible in the exemplary
embodiments without materially departing from the novel teachings and
advantages of this invention. Accordingly, all such modifications are
intended to be included within the scope of this invention.